Biometric Detector and Identity Control Device

ABSTRACT

The present invention describes a biometric detector ( 1 ) comprising an optical sensor ( 21 ), preferably a visible light optical sensor, a surface ( 31 ) against which to lean a fingertip ( 5 ), and optical means ( 3,4 ) adapted to transfer an image of said surface ( 31 ) to said sensor ( 21 ) reducing it in order to detect a fingerprint through said optical sensor ( 21 ); said detector can be advantageously used in an identity control device.

The present invention describes a biometric detector and an identitycontrol device which makes use of it.

Electronic fingerprints detectors have been known for a long time.

Electronic fingerprints detector usually comprises an optical sensor ora capacitive sensor; said sensors are integrated on a chip, i.e. alittle die made of semiconductor material.

Until a few years ago, said detectors were only employed in professionalapplications with very high security requirements.

Recently, in the area of consumer electronics, detection of fingerprintshas started to spread. For example, on the market some personalcomputers and some mobile phones can be found that provide the detectionof fingerprints to control the access (usually known as “login”) to thesystem, i.e. to verify the identity of a user and permit the use of theapparatus only to the authorized user or users; this is an alternativeway or an addition way to input credentials (eg. PIN code orUserID/password) through a keyboard.

Yet, in some cases, the cost of said detectors is still relatively high(as the area of the chip of the sensor is typically about 4 cm²);whereas, in other cases, their reliability and ease of use (particularlyfor the optical sensors of the scanning type) is still relatively low.

General object of the present invention is to provide a biometricdetector which overcomes the drawbacks of the prior art.

Said object is substantially obtained through a biometric detectorhaving the features described in the annexed claims.

Said detector can be advantageously used in an identity control device,in particular for a security system. Said identity control device,having the features described in the annexed claims, constitutes afurther aspect of the present invention.

The present invention will become apparent from the followingdescription to be considered together with the annexed drawings,wherein:

FIG. 1 shows in a schematic way an embodiment of a biometric detectoraccording to the present invention,

FIG. 2 shows in a simplified way a block diagram of a first embodimentof an identity control device according to the present invention, and

FIG. 3 shows in a simplified way a block diagram of a second embodimentof an identity control device according to the present invention.

The following description and the annexed drawings are supplied by wayof non-limiting example.

FIG. 1 shows a biometric detector, indicated as a whole with referencenumber 1.

The detector 1 comprises a chip 2, a small plate 3 made of plastictransparent material, and a lens system 4.

An optical sensor 21 for the visible light, an optical sensor 22 for theinfrared light, together with some other piece of circuitry (not shownin the drawing) for the management of the two sensors are integrated inthe chip 2.

The plate 3 has a first side 31 on which, in the drawing, a fingertip 5of a human being finger is laid against and a second side 32 in contactwith the lens system 4.

The lens system 4 is in contact on the one side with the plate 3 and onthe other side with the chip 2, in particular with the sensor 21.

A detector, as the one shown in FIG. 1, permits to detect fingerprints,as it will be better described in the following. Said a detector (inparticular its sensors) is typically connected to an electronic dataprocessing system; in this way, the fingerprints detected by the sensorcan be stored and processed.

In FIG. 1 the side 31 has a rectangular outline (1.5 cm×2.5 cm) with aperfectly flat development; said side can also have a different outline,e.g. circular or elliptical (similar to the outline of a fingertip);said side can also have a different development, e.g. curved (matchingthe shape of a fingertip). Moreover, the plate 3 could extend more thanrequired by the fingertip itself for reasons not strictly connected tothe detection of fingerprints.

The fingertip is leant against the side 31 in order to enable thedetector 1 to detect a fingerprint.

It is worthwhile pointing out that the detection of the fingerprintcould take place in the same way even if the fingertip shouldn't beperfectly leant against the side 31; however, in this case, there couldbe errors and/or distortion of the detected fingertip image.

Moreover, it is also worthwhile pointing out the fact that the fingertipcould contact only in its peripheral area and not in its central area;in this case, the plate side would have an outline of a frame.

Finally, it is worthwhile pointing out that the plate side of thedetector could be positioned horizontally, vertically or obliquely; thedetector functionality is not influenced by its layout; so saidpositioning will be determined by other factors, such as the ease of useby the user.

The detector 1 shown in FIG. 1 can be advantageously used in an identitycontrol device (e.g. in a home security system, in other words for ahome anti-theft device) as those shown schematically in FIG. 2 and FIG.3.

The identity control device shown in FIG. 2 comprises a microprocessoruP connected to the sensors 21 and 22 of the detector 1. Moreover, themicroprocessor uP is connected to a ROM-type memory ROM, to a RAM-typememory RAM and to a EEPROM-type memory EE (therefore electricallywritable and erasable by the processor uP, but non-volatile). Finally,the microprocessor uP is connected to a transceiver unit RTX for thetransmission and the reception of information to and from a central unitfor example of a security system.

The above mentioned devices can be replaced by equivalent devices; forexample, the microprocessor can be replaced e.g. by a microcontroller,the ROM-type memory by e.g. an EPROM-type memory, the EEPROM-type memoryby e.g. a FLASH-type memory.

The identity control device shown in FIG. 3 differs from the deviceshown in FIG. 2 essentially in that there is no EEPROM-type memory.Moreover, not only does the memory ROM comprise a section PR devoted tocontaining a device control program PR, but also to containing programEN for a fingerprint coding.

An identity control device as the one shown in FIG. 2 or in FIG. 3 canbe located, for example, beside the main door of an apartment and can beused to activate the security system after having left the apartment andto disactivate it before entering the apartment.

In general, a biometric detector, according to the present invention,comprises an optical sensor, a surface where to lean a fingertip, andoptical means to transfer an image from said surface to said sensor. Inparticular, not only is the image transferred, but also reduced by theoptical means.

The optical sensor is preferably sensitive to the visible light; in factfingerprints details are perfectly detectable through said light, i.e.“ridges” and “valleys”.

The sensor receives light reflected by the fingertip surface leantagainst the detector contact surface. Said light can come, for example,from means which generate light and which are integrated in thedetector. Alternatively and advantageously, said light can come from theenvironment in which the detector is located and be deflected anddirected towards and/or concentrated on the fingertip. Known solutionswhich could be used for said illumination are described, for example, inthe U.S. Pat. Nos. 2,899,861 and 5,508,849.

The above mentioned optical means can be made in different ways. Forexample, they can comprise or be constituted by a lens; alternatively,they can comprise o be constituted by more lenses, i.e. by a lenssystem, as the example of FIG. 1.

If the optical means are such to reduce the image from the area of thedetector contact surface to the sensor area, as the example of FIG. 1 inrelation to the surface of the side 31 and to the sensor 21, the area ofthe sensor can be smaller (even a lot smaller) then the area of thecontact surface of the sensor; in this way, the sensor can have reduceddimensions and therefore reduced costs.

The detector according to the present invention can advantageouslycomprise a transparent plate which forms the detector contact surface,as in the case of the plate 3 of the example shown in FIG. 1; said platecan also help to protect the optical sensor and/or the optical means.

The plate is typically flat and it is provided with a first side, whichin the example of FIG. 1 corresponds to the side 31, and with a secondside, which in the example of FIG. 1 corresponds to the side 32; thefirst side is adapted to come into contact with a fingertip and thesecond side is preferably in contact with optical lens means, which inthe example of FIG. 1 corresponds to the lens system 4.

Through the structure described above it is possibile to detect afingerprint of a fingertip leant against the detector contact surface.Nevertheless, said structure does not distinguish between a flesh humanbeing fingertip and a plastic fingertip (that is to say a falsefingertip); nor it can distinguish between a living human beingfingertip and a fingertip of a dead person; nor it can distinguishbetween a fingertip of a conscious person and an unconscious person.

In general, fingerprints detectors, especially for applications in thearea of consumer electronics, cannot make this distinction. This hasbeen so far an underestimated problem and it represents a great defectof said known detectors especially when they are being used, forexample, for identity control devices for security systems.

Therefore, the biometric detector according to the present invention cancomprise further means to check the life status of a human being havinga fingertip in contact with the contact surface of the detector, whichin the example shown in FIG. 1 corresponds to the side 31. Moreover, thebiometric detector according to the present invention can comprisefurther means to check the conscious status of a human being having afingertip in contact with the contact surface of the detector, which inthe example shown in FIG. 1 corresponds to the side 31.

The two checks mentioned above can be provided in different ways. Ofcourse, for application in the area of consumer electronics, ways mustbe used which are simple and economical to provide; in said applicationsthe accuracy of the check can be partially given up in favour ofsimplicity and inexpensiveness.

A first way to check the life status is to detect if there is blood flowin the finger of which the fingertip is leant against the contactsurface of the sensor. This can be done in a very simple and economicalway through an infrared light optical sensor; in fact the blood is hotand therefore it emits infrared light.

A second way to check life status is to detect the heart beat of thehuman being whose fingertip is leant against the contact surface of thesensor. This can be done in a simple and economical way through aninfrared light optical sensor; in fact the amount of blood in the fingervaries with the heart beat

As explained above, the check of the life status can be done with afurther sensor, which in the example shown in FIG. 1 corresponds to thesensor 22; typically, said further sensor in simpler than the sensoradapted to detect the fingerprint. It is clear that the second way ofchecking requires more processing of the signal coming from the sensorand typically a more accurate sensor.

It is worthwhile pointing out that the detection of blood flow enablesto measure blood pressure and/or the tracing of the heart beat.

Not only does the life status be checked from the blood pressure and/orthe heart beat, but a partial identification of the human being can alsobe done; this can be advantageously added to the identification carriedout through fingerprints.

Not only does the life status be checked from the blood pressure and/orthe heart beat, but a human being conscious status can also be partiallychecked.

In the area of anaesthesia, many studies on the conscious status of ahuman being have been carried out. Interesting information and solutionsapplicable to the detector according to the present invention can beobtained, for example, from the U.S. Pat. Nos. 4,788,982 and 6,117,075and 6,801,803.

According to what previously said, the biometric detector according tothe present invention comprises typically one or two sensors; a firstsensor 21, shown in FIG. 1, of the optical type, is required fordetecting the fingerprints of a human being and a second sensor 22,shown in FIG. 1, preferably of the optical type as well, is required fordetecting the status of the human being.

The fingerprint sensor is advantageously integrated in a chip 2, shownin FIG. 1, and preferably of the APS type [Active Pixel Sensor] or ofthe CCD type [Charge Coupled Device]. The APS type is advantageous inthat it can be provided in the CMOS technology; therefore, the cost ofthe chip is limited as the CMOS technology is widely spread, it is easyto integrate in the chip other circuitry for example so as to process asignal provided by the sensor, and the chip consumes little electricpower.

The human status sensor can be integrated either in the same chip, asshown in FIG. 1, or in a different chip. If the two sensors areintegrated in the same chip, it is preferable to have them provided withthe same technology, for example CMOS, or with two compatibletechnologies. If the two sensors are integrated in two different chips,it is preferable to have them being packaged in the same casing.

In FIG. 1, the human status sensor 22 is located beside the fingerprintsensor 21. In fact, both sensors must receive light radiations (both inthe visible band and in the infrared band) from the fingertip 5;therefore, the sensor element or the sensor elements of the statussensor 22 could be located inside the area of the chip 2 reserved forthe fingerprint sensor 21

In order to detect fingerprints, the detector contact surface (side 31in FIG. 1) will preferably have an area included in the range of about 1cm² and 5 cm²; in the case of a rectangular area, the area may be, forexample, 1 cm×1 cm or 2 cm×2 cm or 1.5 cm×2.5 cm or 2 cm×2.5 cm.

In order to recognize a fingerprint, the resolution of detection ispreferably in the range of about 200 dpi and 600 dpi and preferablybetween about 250 dpi and 500 dpi. In the area of criminal justice, ingeneral it is used a 500 dpi resolution. For an application in the areaof consumer electronics lower resolutions can be used, typically around250 dpi but even below 200 dpi. If a low resolution is used, the spacewhere to store the fingerprints is small and the processing and thecomparison between fingerprints is easier as it requires lesscalculations; additionally, the cost of the sensor is low.

In the light of what described above, the fingerprint sensor comprisespreferably between about 50,000 and about 250,000 sensor elements. Theseare preferably disposed as a matrix, for example square or rectangular;50,000 elements correspond, for example, to a matrix 200×250 or to amatrix 225×225; 250,000 pixel may correspond, for example, to a matrix500×500 or to a matrix 400×600.

A sensor as the one indicated above, with present technologies, canoccupy a small area of the chip, for example in the range of about 5 and25 mm² (not only does the area of the chip depend on the sensor but alsoon the further circuitry integrated in it). These dimensions entailoptical means with an magnifying factor comprised between about 3× and10×.

In the future, smaller chips will be obtained; nevertheless, as thedimensions of the fingerprint do not change over time, optical meanswith a high magnifying factor are to be used if very small chip are tobe used.

The biometric detector according to the present invention has beenconceived to be used in an identity control device, in particular for ahome security system (in other words, for a home anti-theft system).

The identity control device according to the present invention typicallycomprises communication means, as for example the transceiver unit RTXshown in FIG. 2 and FIG. 3, adapted to communicate with a central unitfor example of a security system. Said communication can take placethrough a cable system or an ether system or both through a cable and anether system; in the security systems, to connect peripheral devices andcentral unit, it is preferable to use the cable solution as it givessecurity of communication and of connection in a simpler manner. Theconnection between the identity control device and the central unit isused, for example, to transmit fingerprints, requests and/or replies ofthe device, requests and/or replies of the central unit; moreover, theconnection may be used to monitor the continuity of the connectionbetween the device and the central unit to detect possibledisconnections and/or violation of the device.

In the following an identity control device will be described accordingto a first possible embodiment.

According to this first possibility, the identity control deviceaccording to the present invention is adapted to make a comparisonbetween a fingerprint detected by its detector and a set of fingerprintsstored inside the device itself; said set contains the fingerprints ofthe people whose identity has to be checked. The device shown in FIG. 2corresponds to this first possibility.

To store the set of fingerprints it is opportune to use non-volatilememory means, for example a EE memory shown in FIG. 2.

The device can advantageously comprise a processor connected to thedetector, in particular to the fingerprint sensor 21, shown in FIG. 2,and to fingerprint memory means; the microprocessor is therefore adaptedto compare the detected fingerprint and the set of fingerprints. Ofcourse, as common, the microprocessor will typically be connected to aROM-type memory which contains the program for the device control (andtherefore a portion of program for the acquisition of the fingerprintsfrom the fingerprint sensor and a portion of program to carry out theabove said comparison) and a RAM-type memory which contains data to beprocessed. The fingerprints of the people which are to be recognizedhave to be stored in the fingerprints memory means. Said fingerprintscan be inserted in the device by a qualified operator through a suitableapparatus. In alternative or in addition, these can be inserted thanksto the fingerprint sensor itself activating a particular operativeprocedure of the device.

If a human status sensor 22, shown in FIG. 2, is also foreseen in thedetector, the microprocessor will be also connected to said sensor andthe ROM-type memory will contain also a portion of program to carry outthe check on the human being status (life status and/or consciousstatus) preferably each time the fingerprint sensor detects afingerprint.

The device according to the present invention advantageously can firstcheck the human being status and only after, in the case of a positivecheck, make a comparison between fingerprints.

The result of the comparison between the fingerprints will typically besent to the central unit of the security system; this can be carried outfor example by the microprocessor through communication means, as in theexample shown in FIG. 2. Preferably, the result of the comparison issent in a coded format in order to make it difficult to cheat thecentral unit with a false identification.

An identity control device will be described in the following accordingto a second possibile embodiment.

According to this second possibility, the comparison between thefingerprint detected by the device and a set of fingerprints storedinside the central unit is carried out by the central unit itself. Inthis case, there is no necessity for the device to store in a permanentway fingerprints. The device shown in FIG. 3 corresponds to such secondpossibility.

The device can then comprise advantageously a processor connected to thedetector, in particular to the fingerprint sensor 21, shown in FIG. 3,and to communication means RTX, shown in FIG. 3, the microprocessor isthen adapted to send the fingerprints acquired by the fingerprint sensorto the central unit through communication means. Naturally, as usual,the microprocessor will be typically connected to a Rom-type memorywhich contains the control program of the device (and therefore alsoportions of program to carry out the acquisition of the fingerprintsfrom the fingerprint sensor and to send fingerprints) and a RAM-typememory which contains data in the phase of processing.

Memory means are provided in the central unit for the storage of thefingerprints of the people that are to be identified. Such fingerprintscan be inserted directly in the central unit by a qualified operatorthrough a specific apparatus. In alternative or in addition they can beinserted in the central unit thanks to the fingerprints sensor itself(with help of the microprocessor and through the transmission means),activating a particular operative mode of the device and a particularoperative mode of the central unit.

If a human status sensor 22, shown in FIG. 3, is also foreseen in thedetector, the microprocessor will be also connected to that sensor. Inthis case, the check on the status (life status and/or conscious status)can be carried out by the device or by the central unit.

In the case of status sensor, it is advantageous that the status checkis carried out by the device preferably each time the fingerprint sensordetects a fingerprint; to this end, the ROM-type memory will containalso a portion of program to carry out the status check. Only in thecase of a positive check, the device will send to the central unit thefingerprint detected by its fingerprint sensor.

The device could also be adapted to sent fingerprints to the centralunit in a coded format; in this way, for example, it would be moredifficult to cheat the central unit with a false fingerprint (not reallydetected by the fingerprint sensor); in the case of coded fingerprints,the ROM-type memory will contain also a portion of program able toperform such coding; said portion of program is indicated with referenceEN in FIG. 3.

The coding of the fingerprints can be advantageously carried out (forexample, for security reasons and/or for memory space reasons)independently by the fact that the fingerprints are sent by the deviceto the central unit.

The advantageous features of the identity control device according tothe present invention described in the following are independent fromwhere the comparison between the fingerprints takes place.

The identity control device according to the present invention can beprovided (for example programmed) in such a way to acquire at least twofingerprints consecutively; in this way, a user who thinks of being indanger can lean his/her finger against the sensor a first time in orderto make his/her identity be checked and the security system enables theaccess (for example opening or unblocking the home door) and a secondtime in order to signal to the central unit of the security system thedanger. Naturally, it would be better to think of a minimum interval oftime (for example 1 second) and a maximum interval of time (for example10 seconds) between two consecutive finger presses in order to avoidwrong danger signals.

The identity control device according to the present invention can beprovided (for example programmed) in such a way that it realizesautomatically when a fingertip is leant against the detector contactsurface and then proceed with the acquisition of the relativefingerprint.

As an alternative, the identity control device according to the presentinvention can be provided (for example programmed) in such a way toissue, for example periodically, a request of fingerprint to a user;this can be done, for example, issuing a vocal signal and/or displayinga text message which invites the user to lean his/her finger against thedetector contact surface.

The operations described above can be more easily provided under thecontrol of a microprocessor type control unit.

A very interesting possibility is that the device according to thepresent invention issues a request of fingerprint typically only in aparticular situation which will be specified in the following.

Generally, the comparison between two different fingerprints does nottake place comparing directly their two images pixel by pixel, butcomparing their “minutiae”, i.e. characteristic points of thefingerprint which are obtained by processing the “ridges” and “valleys”profiles. The correspondence between two fingerprints corresponds to thematching of a number of “minutiae” included between 12 and 16, accordingto the type of application.

As the device according to the present invention has been conceived forapplications in the area of consumer electronics simple and economicalsolution have to be adopted. Furthermore, one may decide to choose amatching requirement not very strict, for example matching of only 10 or11 “minutiae”. Nevertheless, by doing so, there is the risk of having aFRR [False Reject Rate] a slight high and/or a FAR [False Accept rate] aslight high.

In order to prevent such inconvenience, a strict correspondencecriterion can be used (for example, programming consequently theidentity control device or the central unit of the security system), todetect a fingerprint, to make its comparison with the pre-storedfingerprints, and to issue a request of fingerprints if such comparisonhas lead to a match above a lower threshold (for example, 10 “minutiae”)and below a higher threshold (for example, 14 “minutiae”). Beforedetecting the second fingerprint, the user could, for example, clean thedetector contact surface and/or change finger of his/her free will orunder a solicitation of the device or the central unit.

The identity control device according to the present invention cancomprise one or more further components in addition to those alreadymentioned. The device can comprise a lock (with a mechanical orelectronic or magnetic or optical key); this may be used, for example,to activate or disactivate the security system in the case where thebiometric detector has a failure or a malfunctioning.

The device can comprise a keyboard, this may be used, for example, toactivate or disactivate (through a code) the security system in the casewhere the biometric detector has a failure or a malfunctioning. Thekeyboard may also be used to process device maintenance operationsand/or programming operations.

The device can comprise a display; this may be used, for example, todisplay images and/or visible messages for the user corresponding torequests and/or a warnings and/or errors.

The device can comprise a loudspeaker; this may be used, for example, tosupply the user with sounds and/or vocal messages corresponding torequests and/or a warnings and/or errors.

The device can comprise a microphone; this can be used, for example, toreceive a user's voice; in this way, it is possible to provide a vocalcommand of the device and/or of the central unit or the recognition ofthe user's voice in addition to the recognition of the user'sfingerprints.

From what described, it is evident that the biometric detector accordingto the present invention can be provided in a simple and economical way,without compromising its functionality thanks to the use of opticalmeans which reduce the image to be detected.

Moreover, the biometric detector according to the present inventionenables to reach a high security as it is not only detected afingerprint but also the status of the relative human being.

Finally, it should be noted that the detection of the human status canbe provided without a consistent complexity increase and rise of costwith respect to a detector with detection of the sole fingerprint.

In the present description the identity control device has always beenreferred to being used in a home security system according to thepresent invention.

It is clear that this device can be used also to check the identity of auser of a computer, in particular a personal computer, or of a mobilephone or of a motor vehicle and therefore enabling the access andtherefore the use.

It is clear from the present description, that many other variationswith respect to what described and illustrated herein are possible forthose skilled in the art, without departing from the present inventionas defined in particular by the annexed claims

1. Biometric detector (1) comprising an optical sensor (2), preferably avisible light optical sensor, a surface (31) against which to lean afingertip (5), and optical means (3,4) adapted to transfer an image fromsaid surface (31) to said sensor (21) reducing it in order to detect afingerprint through said optical sensor (21).
 2. Detector according toclaim 1, characterized in that it comprises illumination means adaptedto illuminate a fingertip (5) when said fingertip (5) is leant againstsaid surface (31).
 3. Detector according to claim 1 or 2, characterizedin that said optical means (3,4) comprise lens means (4).
 4. Detectoraccording to claim 3, wherein the area of said surface (31) is largerthan the area of said sensor (21).
 5. Detector according to claim 3 or4, characterized in that it comprises a transparent plate (3) having afirst side (31) and a second side (32), wherein said first side (31) isadapted to come into contact with a fingertip (5) and wherein preferablysaid second side (32) is contacted to said lens means (4).
 6. Detectoraccording to any of the preceding claims form 1 to 5, characterized inthat it comprises means (22) for checking the life status of a humanbeing having a fingertip (5) leant against said surface (31). 7.Detector according to any of the preceding claim from 1 to 5,characterized in that if comprises means (22) for checking the consciousstatus of a human being having a fingertip (5) leant against saidsurface (31).
 8. Detector according to claim 6 or 7, wherein saidchecking means are adapted to detect blood flow inside said finger. 9.Detector according to claim 6 or 7 or 8, wherein said checking means areadapted to detect heart beat of said human being.
 10. Detector accordingto claim 6 or 7 or 8 or 9, wherein said checking means comprises asensor (22), preferably an optical sensor, more preferably an IR lightoptical sensor.
 11. Detector according to any of the preceding claims,wherein said optical sensor (21) is integrated in a chip (2), and ispreferably of the CCD and APS type.
 12. Detector according to claim 11,wherein said visible light optical sensor (21) and said IR light opticalsensor (22) are integrated in the same chip (2).
 13. Detector accordingto claim 11, wherein said visible light optical sensor and said IR lightoptical sensor are integrated in two different chips, said chips beingpackaged within the same casing.
 14. Detector according to any of thepreceding claims, wherein said optical sensor (21) comprises from 50,000to 250,000 sensor elements organized like a matrix.
 15. Detectoraccording to any of the preceding claims, wherein said optical sensor(21) has an area comprised between 5 and 25 mm²
 16. Detector accordingto any of the preceding claims, characterized by detecting fingerprintsat a resolution higher than 200 dpi, preferably higher than 250 dpi, andlower than 600 dpi, preferably lower than 500 dpi
 17. Detector accordingto any of the preceding claims, wherein said surface (31) has an areacomprised between 1 and 5 cm².
 18. Identity control device,characterized in that it comprises a detector (1) according to any ofthe preceding claims.
 19. Device according to claim 18, characterized inthat it comprises communication means (RTX) adapted to communicate witha central unit of a security system.
 20. Device according to claim 18 or19, characterized in that it comprises non-volatile memory means (EE)adapted to store a set of fingerprints.
 21. Device according to claim20, characterized in that it comprises a processor (uP) connected tosaid detector (21,22) and to said memory means, and adapted to carry outa comparison between a fingerprint detected by said detector (1) andfingerprints stored inside said memory means (EE).
 22. Device accordingto claim 21, wherein said processor (uP) is connected to saidcommunication means (RTX) is adapted to send to said central unit theresult of said comparison preferably in a coded format.
 23. Deviceaccording to claim 18 or 19, characterized in that it comprises controlmeans (uP), preferably comprising a processor, connected to saiddetector (21,22) and to said communication means (RTX), and adapted tosend to said central unit a fingerprint detected by said detector (1).24. Device according to claim 23, characterized in that it comprisescoding means (EN) adapted to code a fingerprint detected by saiddetector (1).
 25. Device according to claims 23 and 24, wherein saidcontrol means (uP) are adapted to send to said central unit fingerprintscoded by said coding means (EN).
 26. Device according to any of thepreceding claims from 23 to 25, characterized by the fact that saidcontrol means (uP) are adapted to acquire consecutively at least twofingerprints in order to allow the detection of a danger condition bysaid central unit.
 27. Device according to any of the preceding claimsfrom 18 to 26, characterized in that it comprises control means (uP),preferably comprising a microprocessor, adapted to issue a request offingerprint to a user.
 28. Device according to claim 27, wherein saidcontrol means (uP) are adapted to issue said request if a previousfingerprint matching operation has lead to a match above a lowerthreshold and below a higher threshold.
 29. Device according to any ofthe previous claims from 18 to 28, characterized in that it comprises alock.
 30. Device according to any of claims from 18 to 29, characterizedin that it comprises a keyboard.
 31. Device according to any of claimsfrom 18 to 30, characterized in that it comprises a display.
 32. Deviceaccording to any of claims from 18 to 31, characterized in that itcomprises a loudspeaker.
 33. Device according to any of claims from 18to 32, characterized in that it comprises a microphone.
 34. Biometricdetector and identity control device according to the inventiveteachings of the present invention and of the annexed drawings, whichrepresent preferred and non-limiting examples of embodiments.